Hand tools of the class involved with remote air/hydraulic power booster assemblies are known in the art. In some cases, vacuum retrieval systems for automatically collecting rivet mandrels pulled by the hand tools have been added to existing systems. Such retrieval systems may employ a vacuum pump but usually operate with a constant vacuum supply established by an induction venturi transducer involving a constant drain on the available air supply and, due to inherent restrictions in fittings from the general air supply, contribute to a pressure drop upon operation of the hand tool to perform its mandrel pulling function which undesirably limits the speed of operation and cycle time in setting successive multiple rivets.
The air/hydraulic power units of the prior art normally operate with the air piston in a forward position when the tool is idle drawing the hydraulic end of the piston to create actuating hydraulic pressure multiplied by differential areas. Hydraulic fluid is drawn from a reservoir to fill the chamber at the far end of the hydraulic piston and upon a fast return such oil gushes back into the reservoir frequently causing noise and aeration problems, particularly when the reservoir level is less than full.
The hydraulic piston on the hand tool is normally actuated to draw the mandrel gripping jaws against a return spring at the end of the piston which provides increasing resistance to the pulling force on the jaws and limited decreasing return force on the hydraulic fluid which, together with limited passage openings, tends to create a high vacuum in the return lines with any attempt to achieve a fast return in order to shorten the cycle time.
The limited space available for the return spring in the hand tool has led to over-stressed springs which, upon breaking, score the cylinder walls causing substantial maintenance problems; and the loss of spring pressure upon expansion corresponds to the end of the stroke when the jaw opening creates a need for the most return pressure.
The absence of a fully integrated power supply and mandrel retrieval system in prior art installations has led to relatively bulky total systems rendering protability and mobility difficult and area of operation restricted.